1. Technical Field
The present invention relates to a superabsorbent polymer including a water-soluble salt and a method of preparing the same and, more particularly, to a superabsorbent polymer including a water-soluble salt and a method of preparing the same, wherein the addition of a water-soluble metal salt in the polymerization process of a superabsorbent polymer is very effective at decreasing the concentration of residual monomer (RM).
2. Description of the Related Art
Superabsorbent polymers (SAPs) are synthetic polymers able to absorb water about 500˜1000 times their own weight. Such superabsorbent polymers have actually begun to be used for sanitary items, and are being currently widely utilized in not only hygiene products such as baby disposable diapers and so on, but also in gardening soil repair agents, water stop agents for civil construction, seeding sheets, freshness retaining agents in food distribution sectors, and fomentation materials. Compared to conventional absorbent materials, superabsorbent polymers have an outstanding absorption capacity and thus the market value thereof is increasing with the wider range of applications thereof.
The absorption mechanism of the superabsorbent polymer is controlled by osmotic pressure due to a difference in electric attraction represented by charges of a polymer electrolyte, an affinity between water and a polymer electrolyte, molecular expansion due to repulsive force between polymer electrolyte ions, and interactions of expansion inhibition due to crosslinkages. Briefly, absorbability of the absorbent polymer depends on the aforementioned affinity and molecular expansion, and the absorption rate thereof is greatly affected by osmotic pressure of the absorbent polymer itself.
In order to use the superabsorbent polymer as a hygiene material, the superabsorbent polymer has to essentially possess a low concentration of RM. To lower the concentration of RM, the use of acrylic acid having low dimer concentration is fundamentally adopted, and other methods may also be proposed but are problematic because other properties of the superabsorbent polymer may deteriorate or such additional processing may be complicated.
Therefore, thorough research is ongoing into preparation of superabsorbent polymers having high absorption rate and high absorption scale.